Refrigebating mechanism



Jan. 5, 1'943. G, Mur-'FLY REFRIGERATING MECHANISM Original Filed May25,' 19.37 3 Sheets-Sheet l w .P nu

l l l 3 1 l l l..

Y INVENTOR B6 676m Muff@ 9TORNE/ Jan- 5, 1943- I l MUFFLY i Re. 22,245

REFRIGERAT ING VNXECI-{Ml I SM Original Filed May'25, 193'?.I5`Sheets-Sheet 2 /N VENToR 6,7327); Waff/y A A TT ORNE Ys.

G. MLJFFLY` REFRIGERATING MECHANISM 3 Sheets-Sheet 5 Original vFiled May25, 1937 uf W M m k 6 cal to produce.

mama Jn. s, 1943 BEFRIGEEATING MECHANISM Glenn Mnmy, Bprlngeld, h10

origami No. Serial No.

for reissue Novem 11 Claims. This invention relates torefrigeratingmecha.-

sion of a mechanism of this type that is simple in construction, emclentin operation and economi- Other objects of the invention include the`provision of a sealed type of refrigeration unit embodying certainnovelk features of construction;

the provision of a refrigerating mechanism in-k cluding a rotary type ofpumping mechanism arranged in sealed relation with respect to thedriving motor therefor and provided with a pair of independent suctionpassages one of which is open to the interior of the sealed unit: theprovision of a refrigerating mechanism including a refrigerant circuitat least part of which comprises a plurality of refrigerant paths`connected in parallel and 'a novel form of means for alternatelyopening and closing said paths to the tlow of refrigerant therethrough;the provision of a re-v frigerating mechanism as above described in2,295,124, ama september s, im, maar my z5, 1931.

s, im, semi Nn.

Application 464.350

f the provision ofa gear pump so constructed and nism and lhas for itsprincipal object the proviarranged as to provide for maximum accuracy inengagement of the gears with each other and with their housing with aminimum amount of machining.

The above being among the objects of the :present invention. the sameconsists in certain novel features of construction andV combinations ofParts to be hereinafter described with reference to the accompanyingdrawings,I and then claimed, .having the above and other objects inview.

In the accompanying drawings which illustrate a suitable embodimentof-the present invention and in which like numerals throughout theseveraldifierentviews:

. Figure 1 is a more or less diagrammatic view of a refrigeratingmechanism embodying features of the present invention;

which the controlling means for the parallel paths oi refrigerant floware contained within a sealed refrigerant motor-compressor unit: the

provision of a reirigerating mechanism including a refrigerantcirculatory system at least part of which comprises a plurality ofrefrigerant flow paths connected in parallel and fed with refrigerantthrough a single expansion valve together with means for maintaining thesuction pressure in one of the parallel now paths at a lower value thanin another thereof; the-provision ota refrigerating mechanism having anovel form 'of means associated therewithserving to provide a compressorunloading veect therefor whereby. to enable a smaller driving motor tobe utilized than would otherwise be possible: and the' provision of anew and novel form of oiling mechanism for a refrigerant compressorunit.

.Further objects of the invention include -the provision of a new andnovel form of rotary compressor mechanism for a refrigerating apparatus:

the compressionof gases including gears having a novel form ofco-operating teeth thereon:v

the provision of a new and novel form of gear pump; the provision of arefrigerant comand as type shown in my.

Fig. 2 is an enlarged partially broken, vertical sectional view taken.centrally through a motor compressor unit constructed in accordance withthe present invention and of the type adapted for use in thereirigerating system illustrated in Fig. 1;

Fig. 3 is a partially broken transverse sectional view of the unit shownin Fig. 2 taken as on the line I-I thereof Y I n v Fig. 4 is atransverse sectional view taken on Fig. 5 is an enlarged fragmentaryvertical sec-- tional view taken on the line 5 5 of Fig. 3 andillustrating in greater detail the snap switch mechanism for alternatelyopening and closing parallel refrigerant flow paths of one portion ofthe system;A

Fig. 6 is an enlarged horizontal sectional view taken on the line 6-6 ofFig. 2, illustrating inlet and outlet passages for the pump mechanismlocated in the unit;

Fig. 7 is an enlarged fragmentary vertical sectional view taken on theline 'I--1 of F18. 4: Fig. 8 is an enlarged fragmentary vertical sec-,tional view taken on the line'v 8 8 of Fig. 4;

Fig. 9 isa more or less diagrammatic view illustrating in greater detailthe particular shape and arrangement or the'teeth of the gears in thelcompressor unit: and,

Fig. lois 'a fragmentary, vertical sectional view e of a modified formof construction.

Although certain features of the present lnventionare applicable torefrigerating systems of more or less conventional type. certainfeatures thereof in particular are specially adapted for use inconnection with refrigerating systems of the Letters Patent of theUnited refer to like parts' States for improvements in Refrigeratingmechanism. Nos. 2,145,773; 2,145,774; 2,145,775, and 2,145,777, 'allissued January 31, 1939. In my above identified patents means arev shownprovided for alternately refrigerating diiferent groups of ice makingsurfaces whereby to cause ice to be formed alternately by said groupsand which ice is adapted to be melted free of its surfaces duringthattime when it is not being refrigeratedV and during which time anothergroup of ice mak-` ing surfaces is being refrigerated. In my aboveidentified patents these ice making surfaces are positioned within aninsulated cabinet wherein the air within the cabinet is adapted tocontact a water tank and certain of the refrigerated surfaces of themechanism and to be cooled to a desirable degree thereby for the properpreservation oi` food stuffs within the cabinet. 4

Additionally in my above identified patents the refrigerant passingthrough the evaporator associated with surfaces being refrigerated atany particular moment is shown` as also passing through anevaporatorassociated with a chamber positioned within the refrigerator cabinet anditself insulated against exchange of heat with the bulk of the air,within the cabinet whereby to provide a sub-freezing chamber or thelike. In accordance with the present invention the alternatelyrefrigerated evaporators of a similar ice f maker are similarlypositioned to also cool `the air within the cabinet but instead ofemploying the refrigerant passing therethrough to produce arefrlgerating effect in a sub-freezing chamber within the cabinet, arefrigerant path of now par.- allel Vtothe path of iiow to the ice makeris provided for the sharp freezing (sub-freezing) chamber and, as in myprior constructions, the sharp freezing chamber is preferably itselfinsulated from the exchange of heat between the air within it and thatcontained generally within the main food storage space of therefrigerator cabinet.

In order to more fully explain this system reference may be had'toFig. 1in which the numeral 20 vrepresents the housing of a sealedmotor-compressor unit enclosing a suitable p'ump mechanism generallyindicated at 22 which, ln

vthe broader aspects of the present invention, may

beof anysuitable type but a specificfo'rm of which is more fullydescribed in connection with the remainingviews and forms van importantfea- D ture of the present invention. The pump 22 is 'provided with asingle refrigerant discharge line 24 which leads into the bottom of acontainer 25 the upper end of which is connected to a conventional typeof condenser 28 provided withfa conventionalreceiver 38 at its loweredge. A tube`32 connectsthe receiver 3i) with a single expansion valve34. yAlthough the discharge side of the expansion valve 34 may beconnected to any suit l able evaporator suitably arranged inco-operative relation with respect to a water container for causing iceto be formed therein, or employed for any other purpose, in order toillustrate the application of the present invention to structures of thegeneral type disclosed in my above identitled patents, .the expansionvalve 34 is shown as being connected by a tube 38 and a suitable branchtube 38 with a pair Vof evaporators and i associated Water containerindicated diagrammaticallyat 40 arranged to provide parallel refrigerantow paths and each of uwhich may be assumed to be associated with acorresponding group ofice making surfaces for the purpose of freezingthe water intoice. Each of the evapo- 1 sarily bothy at' one time.

rators 48 is provided with a discharge duct 42 .each of which terminatesindependently of the other thereof4 within the housing 20.

Within the housing 28 a valve mechanism indicated generally at 44 inFig. 1 is provided for alternately closing the discharge ends of thetubes 42 to the flow'- of refrigerant'therethrough and suitablemechanism is provided as will herelnafter be specifically describedinconnection with other viewsA of the drawings for operating the valvemechanism 44 at timed intervals to a1- ternately close and open theducts 42 thereby to render the evaporator connected with theiclosed ductinoperative for refrigerating purposes and rendering the evaporator 48connected with the open duct open to the flow of refrigeranttherethrough and thereby operative for refrigerating` y purposes. Aspreviously mentioned the compressor 22 is provided with a pair ofindependent suction ports one of which is open to the interior of thehousing 28 and acts to withdraw refrigerant from the interior of thehousing ,20 and consequently from that evaporator then opened into theinterior thereof, such refrigerant being drawn into the pump 22 to becompressed and then discharged through the outlet duct or discharge line24.

It will be understood that the evaporators 40 are positioned within aninsulated cabinet indicated at 5|) and' exposed to contact with the airtherein for the purpose of cooling such air thereby to preserve foodstuffs contained in the cabinet. Within the cabinet is a smallerinsulated chamber 52 within whichy is positioned an evaporator 54connected by a tube 58 with the other and remaining suction passage ofthepump 22. The inlet side ofthe evaporator 54 is connected with theduct 35 on the discharge side of theexpansion valve 34 through apressure reducing device which may conveniently be either a capillarytube 58 or a weighted valve device 58, both being shown connected inseries in Fig. 1 merely as'a matter of illustration as either one or theother thereof will be employed, but not neces- The weighted valve ispreferred as -it always imposes a predetermined additional pressurereduction to the evaporator 54 IWith the construction thus far describedit will 54 and, because of the:` restriction 58 or 58 in f the feed lineto the evaporator 54, the suction pressure of the pump applied to theevaporator 54 will be lower than that applied to the evaporators 40 andconsequently the evaporator 54 will be maintained at a lower`temperature than the temperature of the evaporators 40 thereby topermitthe interior of the chamber 52 to be maintained at a substantially lowertemperature than the interior of the cabinet 50.

perature ofthe chamber 52 maybe maintained somewhere between zero andplus 10 F., that the interior of the cabinet 58may be maintained at atemperature somewhere between 40 vto 45 F. and that the evaporators 48will be maintained during their respective'refrigerated periods at atemperature of somewhere between plus 15 and v As a matter ofillustration it maybe assumed that the temdischarge line 24' frigerantin the condenser 25"y F. and that the evaporator 48net. beingrefrigerated and being warmed by the air vinthe cabinet 884s somewherebetween'the temperatures oi' 82"` and 45?` F. It will thus be apparentthat by the employment of a simple restrictingy The chamber 28 isprovided with a check valve 18 in its discharge sidepermittingflow offiuid through it towards the condenser 28 only. When the pump 22,stop'sat the end of each cycle of operation the-refrigerant under pressure inthe and container 28 will gradually be equalized with the low pressureside of the refrigerating system due to reverse rotation of and leakagethrough the pump 22 which is not equipped with valves,but the highpressure re- 28 andreceiver 88 will be prevented from being transmittedvinto the container 28 and housing 28 by thecheck valve 18. ConsequentlyVat the beginning of the next cycle of operation of the pumpA 22 it willbe initially pumping against a pressure substantially equivalent to thatinthe suction or lower pressure side of the system and there will besubstantially no head for the pump to pump against upon initiation ofoperation. By suitably proportioning the chamber 28 to obtain therequired volume assurance may driving the pump 22 will reach its normalspeed of operation prior to a 4material or a normal operating pressureexisting in the discharge line 2l. Shortly after the pump normal speedof operation, if the chamber 28 is properly proportioned, the pressureof the compressed refrigerant in the discharge line 2l will equal thatin the high side 'of the system after `which the check valve 18 willlift and normal operation of the system will begin. The effect of theconstruction is, however, as will be readily understood by those skilledin the art, to serve the same purpose as the usual compressor unloaderfound in refrigerating mechanisms and provided for the purpose ofpermitting the motor which drives the pump to attain its normal or thechamber 28 between the outlet GII .spect to the gear 88 noted that thecompressor unit includes the inverted generally cup-shaped pressed metalhousing 28, the lower end of which is closed by the round base member 88of the pump 22 and which l is hermetically sealed thereto as by weldingalong the aligned lower edges thereof as at 82. or otherwise. Within thehousing 28 and seated upon the base 88 is an intermediate pu`rnp bodysection 88 provided with three cylindricalopenings therethroughpreferably arranged with their axes in a common plane as shown in Fig. 4and with adjacent peripheral portions ofv adjacent openings inintersecting relation, the central opening containing a -gear 88 and theopposite end openings containing the gears 88. Overiying theintermediate pump-body portion 84 is a cap member 82 provided with anupwardly extending hollow boss 84 concentric with the gear' 88 and theopening therefor and serving to rotatably receive therein an upwardlyextending shaft 88 the lower end of which is-suitabiy fixed with refortransmitting driving movementfthereto and the upper endv of which hassuitably fixed theretoA the rotor 880i an electric motor having 'astator |88, the stator |88 being suitably received and secured withinthe upper vand reduced end portion of the housing 28 as by a press fittherein. Studs |8| threaded :inA

be had that. the motor 22 has attained its substantially normal speedbefore thefull burden of the .pumping operation is placed upon it. The

provision of such a means is of advantagein that a motor is not requiredto develop the torque that it would otherwise have to develop ifirnmediateiy subjected to the pressure of the high side of the systemupon initiation of its driving movement. The result is that a lessexpensive motor may be employed with equally satisfactory results. Itmay be noted. incidentally. at this point, that if desired an `oilbaille such as 12 may be included in the chamber 2 8 for the' inil'llose` of reducing the otherwise normal no w of lubricatingl oil withthe refrigerant owing through the evaporators. the oil'separated outfinsuch casel beini carried back into the pump 22 during inoperativeperiods lof the pump. due' to the pressure equalizin'g. action abovedescribed.

Referring now tothe remaining gures in the--l drawings and particularlyto Fig. 2 it will Ibe V peripheries of into the base plate 88 andextending through the pump body 8l and cover plate 82 serve to secure ythese parts together. 4

The leads to the electric motor are carried throughsuitableconnectionsindicated at |82 in Fig. 2 extending out through the walls ofthe i housing 28 and hrmetically sealed thereto `in' a conventionalmanner to prevent leakage of gas thereabout. As indicated in Fig. l andin accordance with conventional practice three leads, namely |88. |88and |88 are provided for the motor 88|88, the leads |88 and |88 beingconnected to conventional power lines I|8 and ||2 through a conventionalthermostatic switch structure Ill arranged within'the cabinet 88 I andoperated by variations in temperature therein for the purpose ofcontrolling the cyclic operation of the compressor unit. The lead |84which extends to a suitable starting-winding circuit (not shown) extendsthrough a starting circuit breaker ||8 Ain accordance with. conventionalpractice and then to one of the power lines ||8 or lf2.

It will be understood that the gears 88 and 88 lie in meshingrelationship. The arrangement of the-three gears 88 and 88 is such asto" provide two independent gear pumps as far as suction eiect isconcerned; In other words the gear 88 and either one of the two gears 88co-operate to form a gear pump in accordance with conventional gear pumppractice'and the gear 88 co-operates with theother gear 88 to provide adiere'nt gear pump in accordance with conventional practice, except thatthe two pumps intermingle their discharges and are, therefore.

to he considered as one pump on the discharge side. Referringparticularly to-Fig. 4 if the gears to each other and will be carriedaround the outer trapped around the gears in a counterciockwisedirection and being squeezed o ut the gears, that portion of the fluid'A between the teeth ofA the gears 88 being *carried completely `frombetween the gears l88 and the gear 88 point of intersection of thewalls' of theY openings for the |30 for the sans y at the points wherethe teeth on the gears come into mesh ywith each other. The gas trappedbetween -the teeth of the gear 88 as such teeth leave meshingrelationship with the teeth of one of the gears 88 will be' carriedvaround in a clockwise direction as viewed in Fig. 4 and will besqueezed out therefrom at the point where the teeth of the gear 88 meshwith the teeth of the other gear 88. Consequently with a gear pump ofthe type shown` while the gear 88 and one of the gears 88 co-operate toprovide a suction inlet which is entirely independent of the suctioninlet formed 88, nevertheless the iluid which is drawn into the. inletformed between the gear 88 and one gear 88 will be carried aroundcommingled'with the gas or other fluid inlet between ythe gear 88 andconsequently there would be noparticular point in attempting toseparate-the discharge ports |34 and |42. In accordance with the above asuction inlet for the `88 and one gear 88 is sage |38 drilled downwardlythrough the upper casting 82 of the pump, as indicated in Fig. '7, andmeets the top wall of the pump body 84 at the point where the walls of1the openings in the body 84 for the gears 88 and 88 intersect above theplane of the gear axes as viewed in Fig. 4 and Walls is beveled of! asindicated at |32 in Figs. 4 and 7 to provide an ample path for the ilowof iiuid over the full width of the teeth of the gears 88 and 88 at thispoint. Inasmuch as the passage |38 is open to the inside of 28, theopening |38 may be made desired and may even be enlarged to the extentof eliminating, all of that part of the top plate 92 except immediatelyover the area where the teeth of theassociated gear 88 begin to and aslarge as actually mesh with the` teeth of the gear 88 as4 willhereinafter be.- brought out in connection with Fig. 10. Likewise suchpart of the body84 surrounding" such gear 88. not required for bearingon the periphery of the gear to in place may also be eliminated. Theopposite of the open- 88 and 88 are received |34 drilled downwardly oflthe pump and which ings in which the gears is open to a blind openingin the bottom plate 88 1 terminates "adjacent the lower end of adownwardly projecting boss |138 formed centrally of the bottom plate 88.The point where the walls gear 88 and the other gear 88 in the chamberplate 84 intersect` adjacentr` the point where the teeth of these gearsI88 and 88 leave meshing relationship with respect to each other whenturning in the direction indicated inFlg. 4 is open to a blind opening|38, best shownin Figs. 4 and 8 drilled downwardly in the bottoml plate88 of` the pump to a point adjacent the lower face of the boss |38 andwhich thus serve as the second-suction in-..

let for the pump. As in the case of the inlet pump formed by the iirstpair of gears 88 and 88 the body at the point where the walls of theopenings therein for the gear 88 and the other gear 88 meet in alignmentwith the outlet passage|38 is beveled of! as at |48 to permit accessy offluid entering through the inlet passage |38 over the fullV width" ofthe teeth of the gears. l L Y The-discharge side of the pump formed bythe gears 88 and 88 provided at the points where between the gear 88 andthe other gear which is drawn into the. "88 and the other gear.

pump comprisingithe gear formed by a drilled "pase the housing` maintain1ry the teeth of these gears enter meshing relationship with respect toeachother when rotating in the direction shown in Fig. 4 is providedwithoutlets in the/form of blind openingsl |34 and |42 drilled downwardly inthe base plate 88 to points adjacent the lower end ofv the'boss |38 pumpextends upwardly through the cover plate that it opens to theinterior t30V` thispoint of intersection of theseV illustration `shown to` the vof the housing 28.

from and higher than Vmentioned this ability as best brought out inFigs.

4. '7, and 8. As indicated in Fig. 6 within the lower portion f thevboss |38 the lower ends of the discharge passages |34 andv |42 `areconnected togetherY by a pair of convergent horizontally directedpassages |44 and |48, respectively. to a common outlet passage |48connected in the particular discharge line 24 previously described. Thesuction connection |38 for; the pumplformed by the gear 88' and` the`righthand gear 88 is connected in the lower portion of the boss |38with a transverse passage |58 suitably connected in the case illustratedwith a suction line 58 for the evaporator 54. Because of the fact thatthe suction passage |38 for the 92 it will be apparent The suction ducts42 for the evaporators 48'open into the interior of the housing 28independently of oneanother through suitable drilled passages |54drilled upwardly through the base plate 88, body 84, and cover plate 92of the pump and the lower ends of which are respectively connected tothe suction lines 42 `o1' the two evaporators 48. It will, accordingly,

be understood in the construction shown that the refrigerant dischargedfrom the evaporators 48 is carried into the interior of the housing 28from which it is discharged through the intake passage I 38 for the pumpformed by one pair of the gears 88 and 88. 'Ihe pump thus formed bythese two gears provides means for impressingthe suction side of theevaporators 48 with a suction pressure which may and will be in theconstruction shown y under. normal operating conditions ldiiierent thesuction pressure which discharge side of the evaporator 54 through thepump formed by the lgear 88 and the other gear 88, refrigerant pumped byboth of such pumps, however. commingling with each other in the pump andbeing discharged therefrom in a single stream by means of the passagesAbest shown in Fig. 6. As previously of the pump to provide formaintaining two entirely independent suction pressures` of differentvalues enables the evaporator `54 to be maintained under a normally isimpressed upon the lower temperature than that at which one or `theother of the evaporators 48 is maintained.

The pump thus described is novel inI further respects than thoseheretofore brought out. For instanceit will be noted that the gears 88are not provided with a shaft or journal about which they operate as inconventional constructions.

trappedtherein. 'Ihe holes |8| are provided in `the gears 88 only'forthe purpose of ease in manufacturing and once the gear is nished, theholes beingno longer necessary are plugged as described.

tained in proper meshing spect to the gear against the walls of in thebody 84 and ings are made a. fairly accuratet with respect tothe'circumferences of the gears 88 and the The gears 88 aremainrelationship with re-V 88 by peripherally .bearing for its operationthey wide lands as indicated in Fig. 9, which thus prog 22,245 teetn oftheI gears l are provided with unusually vide ample bearing areasbetween the peripheries of the gears and the walls .of the openings vinwhich they are received. The elimination of the shaft or journal for thegears BB not only makes the pump more economical to manufacture inlessening the number of parts and machine operations required, but themachine operations themselves are simplied and rendered more economicalby reason of the elimination of the accurately aligned holes in the baseplate 00 and top plate 92 which would otherwise be required for theshafts of gears I8 and this permits manufacturing tolerances in theconstruction shown to be maintained at wider limits than would otherwisebe possible in quantity production. l

The use of a gear type pump as a compressor is old, but in all pastusages, as far as I am aware, the gear pumps designed for use ascompressors have been at fault in being so designed that two mating gearteeth cannot possibly have involute curves throughout the length oftheir engagement.

Since the involute curve cannot extend below the base circle of a gear,it is obvious that in order to have an involute curve extend to the rootof a tooth or anywhere nearly to the root of the tooth, the gear musthave a large number of teeth or be designed with an unusually largepressure angle.

' A common proportion used in gear type compressors in the past has beena gear of l0 to 16 diametral pitch having ten or twelve teeth. In a i6pitch gear, the depth of engagement between g the two gears is l/a of aninch, or normally of an inch above and below the pitch circle on eachgear. These gears would have pitch diameters of one inch or'less, evenwhen they are cut at a con-v siderable helix angle. They have ordinarilybeen designed with a 141/2 pressure angle, but even if the pressureangle were increased to 20, we ilndA -that the base circle diameter of agear having a one inch pitch diameter and a 20 pressure angle is only.9397", which figure is the cosine of 20,

` and the base circle diameter is the product of the pitch diameterandthe cosine of the pressure angle.

With a gear of this type. the involute curve can extend only about .030"below the pitch circle. As this is true of each gear, it provides adepth of only .060" out of the total working depth of the teeth in whichthe mating teeth can possibly engage each other on involute curves.

Anotherfault ot all gear pumps employed as refrigeration compressors inthe past, as far as I4 am aware, is that the usual clearance commonlyprovided in all types of gearing has'been allowed at the bottoms oftooth spaces. This clearance is provided for in the makinglof stock gearcutters and hobs, but is undesirable in a pump which is to be used forthe purpose of compressing a gas because it leaves a dead space" ofcompressed gas which cannot be forced out through the discharge L portand the work perfumed upon which by compression is substantially lost. v

A third fault which has been present in most of the gear typecompressors designed thus faris the use of helical teeth. Inventorsanddesigners have been under the impression that the helical. teeth causethe gas to beforced lengthwise of a tooth space, and compressed at oneend of the helical gear or at the middle of `a herring-bone gear. Thisis an erroneous conception, the fallacy of which may be seen inconsidering a sectional view taken normal to the teeth of a pair ofmating gears, having helical teeth. It will be seen that in addition tothe clearance space at the bottom of each tooth space, there is a.considerable passage allowed for now of the gas longitudinally of atooth space, even when both teeth are properly engaged with a tooth ofthe mating gear. This means that the gas, instead of being compressedtoward the end at which it is to be dis-'- charged, is allowed to escapeto the opposite end of the tooth spaces of the two mating gears, andthere is considerable inemciency in pumping for this reason.

` In the design of the gears for the compressor shown herein the faultsof previous designs in the above respects have been overcome byselecting proportions and sizes of gear teeth to provide of gears; toprovide for a minimum amount ofl clearance between the point of onetooth and the bottom of the space between teeth of the matins gear; inproviding for an overlapping of the arcs of working contact ofsuccessive teeth; and in using straight spur gears instead of helicalgears.

A- simple mathematical formula for providing involute curves throughoutthe full 'depths of driving contacts between teeth on each of the pairof gears is that the base circle radius of either gear must not exceedthe radial distance from the center ofthe gear .to the point oiintersection of the outside diameter of the gear mated therewith inrunning position and one of the internaltangents common to the basecircles of the two gears. vThe two popular pressure angles used on gearsare 141/2 and 20, and the cosine is smaller for the greater angle. Thepair of gears 86 and 88 shown in detail in Fig.

` .9 are designed to accomplish the desired result.

are fifty-nine teeth on the right hand or driv ing gear 86 and sixty-oneteeth on the left hand or driven gear 88.' The outside diameters of thetwo gears are the same.' and they are as-v sumed to have been cut withthe same hob, which is specially'designed to allow a minimum ofclearance between' the points of the teeth and the bottoms of the spacesbetween the teeth of the mating gear. Since the base circular pitch mustbe the same on the two gears,

the base circle of the nity-nine tooth gear 86 is {5%1 oi' the basecircle of the sixty-one tooth gear 8l. The depth of teeth is the same onthe twogears. Due -to the large number of teeth there will be' two ormore pairs of teeth engaged in driving contact in one direction atalltimes, thus providing a seal against the ilow of gas from the deliveryside to the intake sidebetween the meshing gears. This condition ismathematically impossible on gears of theproportions that haveheretofore been used in gear type compressors designed for refrigeratingsystems. It is not necessary to go to the extreme illustrated by Fig. 9,but it is necessary that the base circle fall inside of the smallestcircle at which a tooth contact is made on either gear. In other words,on' either of the two straight lines i60 which form the internaltangents of the two base circles, there must always be one and thereshould be two or more points of driving contact between involute curvesof On the gear 8B at the ber of teeth necessary to meet thisrequirement, and this regardless of whether they gears v.

are of equal diameter, the base circular pitch, which must be identicalin both gears,A must be less than the length of that part of an internaltangent of the two base circles of the pair of mating gears cut olf by`the outside atdiameter circles of the two gears. It is desirable to havetwo teeth in working contact at all times which requires that the basecircular pitch of the gears be less than half of the above definedportion of the internal tangent.

`In the example shown in diameter of each gear blank is that of a normalsixty tooth gear. Because the driving gear 88 is cut with fifty-nineteeth, its base circle is reduced in diameter so that the tooth flanksare formed by parts of the involute curve econsiderably removed from thebase circle. .On the sixty-one tooth driven gear 88 shown at Fig. 9, theoutside the left of Fig. 9, having an outside diameterv which would benormal for a sixty tooth gear,

`the base circle is still insidel of the bottom diameter circle in thisexample, but' 'the tooth flanks are developed byportions ofthe involutecurve which are much closer to the base circle. This means that duringthe process of generating the two gears from the same hob, the gearblanks are driven at different ratios to the hob rotation. When the twogearsthus generated are engaged with each other, it will be found thatthe pitch circle of the sixty-one tooth gear 88 falls nearer to theoutside diameter, whereas the pitch circle of the fifty-nine tooth gear86 falls nearer to the bottom diameter.

The design of this pair of gears as before outlined would accomplish itspurpose with either one of the two acting as the driver, but for thepurpose of this design the fifty-nine tooth gear 86 is employed as thedriver and the sixty-one tooth gear 88 as the driven gear for reasonspreviously described.` It will be noted from Fig. 9 that the lands atthe tops of teeth on the y sixty-one tooth gear .88 are greater than thelands at the tops of the teeth on the fifty-nine tooth gear 85. This isa result of the method of generation previously explained.

Since the driving gear 86 has an odd number of teeth and the two drivengears 88 are ideno tical with each other, it willbe seen that thedischarges of gas at the two points of the gears entering engagementwill occur alternately. While this is not an essential of the design, itis desirable in providing a more continuous flow of compressedrefrigerant to the condenser and breaking up the sound of gas dischargesfrom the compressor. Likewise, the suction impulses occur alternately,there being lliil suction impulses in the two separate suction passagesand 118 discharge impulses directed into the one discharge passage |48leading to the condenser vper revolution of gear 86. i

In order to operate the valve mechanism indicated generally at 44 inorder to alternately open and close the suction lines 42 for theevaporators 48, the boss 84 for the top plate 82 of the pump is providedwith a'laterally extending boss |18 best shown in Fig. 3. A shaft |12arranged with its axis in perpendicular relationshi-pto the axis of theshaft 88 is xed Withinthe boss |18 and projects laterally outwardlytherefrom. A rocker element |14, best shown in Fig. 5, is pivotallymounted upon the shaft |12 in overlying relationship with respect to thepassages |54 consuction lines 42. Each end of the rocker memberf|14 hasthat when direction so as to `bring one of the valves |16 into sealingrelation with respect to the corresponding passage |54, the other valve|1515 lifted from its passage |54 so as to open` the latterpassage tothe interior of the casing 28.

The rocker |14 with its valves |18 is caused to alternately pivot inopposite directions by means of the following mechanism. -An arm member|18 is pivotally connected by means of a pin |80 to a side face of thecasting 92 of the compressor for swinging movement in a vertical p lane.The upper end of the arm |18 is bent laterally and `then downwardly toprovide4 afdownwardly directed projection |82. The rocker |14 is pro-`vided with an 'upwardly directed projection |84 extends between and ismaintained under compression between the projections |82 and |84. Thearm 18 is provided with an elongated aperture |88 ceived a cam |98mounted for rotation therein in a manner which will hereinafter be fullyexplained. Upon rotation of the cam |98 from the position indicated inFig. the point of the cam |88in turning will eventually strike againstthe lefthand side of the slot |88 and cause the arm |18 to be pivoted inacounterclockwise direction of rotation, as viewed in Fig. 5, until theprojection |82 thereof passes over to the left of a plane including thelaxis of the shaft |12 and the point of the projection |84, whereupon,the force .of the spring |88 will cause the rocker |14 together withthe valves thereon to pivot in a clockwise direction of rotation asviewed in Fig. 5 about the axis of the shaft |12 and will raise thelefthand valve |18 and move the righthand valve |16 downwardly intosealing relation with respect to the corresponding passage |54, themovement of the arm |18 to the left or in a counterclockwise directionas viewed in Fig. 5 being limited by the righthand wall of the slot |88striking against the cam |88. the cam |88 will thereafter graduallycause the arm |18 to pivot in a clockwise direction of rotation aboutits pivot pin |88 until the point of the projection |82 passes to theright of a plane includingthe axis of the shaft |12 and the point thismechanism constitutes a snap mechanism operated through rotation of thecam |88 to alternately cause the valves |16 to be snapped between openand closed positions with respect to their respective passages |54. i

In order to operatethe cam |88 so that the time of activity of each ofthe evaporators 48 will be sufficient to cause freezing of a desiredthickness of ice or a desired maximum limit of frost accumulation and toinsure melting of the ice or frost thus formed during each inoperativeperiod of each of the evaporators 48 the following mechanism isprovided. Secured on the shaft 88 immediatelyV above the boss 84 bymeans of a pin 28| passing through the hub portion there- A necting theinterior of the housing zo vwith the Y loosely secured thereto a valvemember |18, the `relation `of the parts being such the rocker arm |14 ispivoted in one- A coiled. spring |86 therein within which aperture isrel Continuing rotary movement of .a gear reduction of such natureThis-worm 202 is shown as'being of a more or-less hypoid type and may beconsidered as one end portion only of a conventional Hindley worm. Theworm 202 is arranged in meshing relationship with a gear 204 arrangedwith its' axis in a horizontal plane and rotatable with its shaft 206,best shown in Fig. 3, having bearing in a suitable boss 208 formed onthe upper face of Y the top member 82 of the pump 22. The opposite endof the shaft 206 is formedto provide a single thread worm 2|0 thereon.It will be noted from an.inspection of Fig. 3 that the bore' in the boss208 for theshaft 206 is enlarged at the worm end of the shaft and thecorresponding end of the worm 2|0 projects into such enlarged boreportion for a purpose which will hereinafter be more clearly broughtout.

shaft 2|4 opposite the worm wheel 2|2is providedwith afsingle threadworm 2|.8 which lies in meshing relationship with respect to a helicalgear or worm wheel 220 freely rotatable upon the outer end of the fixedshaft |12 outwardly of the arm |18 and to which gear or worm wheel 220the cam |90 is fixed for equal rotation theref with. The train of gearsthus provided between the shaft 96 of the motor 98|00 and the gear 220to which the cam |90 is secured preferably provides that the cam |90will make one complete revolution during each sixty 'or more minutes ofcontinuous operation of the motor -98-l00. The figures selectedl in thedesign Y shown is eighty minutes which is suitable for one particulararrangement of refrigerating mechanism of the type shown, but obviouslythis figure may be varied by varying the ratio of the gear traindescribedto obtain any desired ratio of movement between the drivingmotor and the cam |90.

vLubrication of the moving parts of the compressor unit is accomplishedin the following manner. As in substantially all refrigerating systems aquantity of lubricating oil is introduced into the system and in thepresent case the lower 20 provides a reservoir for part of the casingthe main body of lubricatingoil which is indicated at 230. Thelubricating oil 230 is of such a depth as to immerse the lower portionof the worm wheel 2|2 therein so thatl the worm wheel in rotating willcarry oil up with it into contact with 'the worm 2|0. The pitch of theworm 2|0 is preferably such in relation to its direction of rotationthat oil be carried towards the in Fig. 3 and into the enlarged portionof the bore for the shaft 206.7 The oil which is carried into the borein the boss 208 for the shaft 206 will,

of course, provide lubrication for the shaft 206..

Additionally, it will b noted from an inspection of Figs. 2 and 3 that apocket 232 is provided -in the upper face of the casting 92 of thecornpressor into which pocket 232 the lower portion of the worm wheel204 projects. The boss 208 is provided with an oil 'lead 234, indicatedin Figs. 2 and 3, which leads from the junction of the large and smallportions of the bore in the boss 208 for the shaft 206 into the pocket`232 and thus provides a means whereby the pocket 202 is filled with oil.The'worm wheel 204 in deposited thereon will tend to top of the sheet asviewed rotating Vcarries oil upwardly contact with the worm 202, therebyto lubricate motor compressor unit therewith and into the rubbing facesbetween the worm 282 and worm wheel 204. Further. as illustrated inFig.- 2 the periphery of the worm wheel 284 extends into almostcontacting relation with respect to the outer surface of the boss 94 onthe cover plate 92 and adjacent this point of almost contact the boss 94is provided with y wardly extending passage 236 the edges of which areadapted to wipe off lubricant from the periphery of the worm wheel 204which as will be understood will be rotating at a fair speed of rotationand, therefore, tendto throw the oil thereon to the outer peripherythereof, andin this manner oil is carried to the bearing in the boss 94for the shaft 96. The oil passing into the passage 236 will, of course,lubricate the upper bearing of shaft 96 and be carried on downwardlyinto the pump whereby to effect lubrication of the wearing surfacesthereof. Additionally, it will be understood, of course, as in allconventional -constructions the refrigerant will carry a certain amountof entrained ,lubricating oil along with it. in circulating through thesystem and this, together with the movement of the parts in the housing20, will tend to createa certain amount of ail vapor in the housing 20which will be drawn into the compressor 22 through the inlet passage |30and thus provide an additional supply of lubricant for the working partsof the pump.

In Fig. l0 a modification of the above described is shown illustrating apreferred construction thereof not particularly designed for use invconnection with parallel evaporators such as the evapoxatorsA 40 intheprevious views. As will be apparent under such circumstances, `it is notnecessary to provide any control'rneans for the alternated connection ofa. pairof suction passages with the interior of the casing,. andconsequently the gearing previously'described for the operating cam 90may be dispensed with, but in such cases a different type of oilingsystem must be provided.

Referring to Fig. l0 in which parts correspond- 'ing to the partspreviously described are indicated by the same numerals except that suchripheral portion of the base plate with the in-A terposition of asuitable gasket therebetween.

Studs 252 secured in the marginal portions of the base plate 80 projectup through the flange 250 land receive thereon nuts 254 for the purposeof drawing the flange 250 into sealing relation with respect to thebaseplate. Nuts 255 are'preferably threaded upon the downwardly projectingends of the studs 252 below the base plate 80' and preferably threequally angularly spaced studs 252 are further provided with lock nuts256 below the nuts 255 onto the periphery of which the upper ends ofcoil springs 258 are threaded. The coil springs 258 serve'as a resilientsupport for the motor compressor unit.

In this case the base 88' instead ofV having a flat upper surface isprovided with a raised central portion 259 providing anoil sump betweenits periphery and the casingy 20 in which the oil 230 is received. Itwill be noted that the level of the oil- 230' the portion 259. AThe tube262 havingone end open to the oil 230' in the sump extends upwardlyltherethrough and projects through the wallof the a downwardly and in-vis below the upper edge of f tube 26| where its end f cause oil to bedrawn through the screen.

,268, the bottom portion of vof' the-shaft 96' directly,'as at 212,

of the refrigerant flow walls of the tube therethrough, and the 260inapproximate transverse alignment `with the upper en d of the tube 262is preferably compressed inwardly as at 264 to effect a venturi throughthe tube 280 will createa sumciently low pressure yat the dischargekendof the tube 202 to 266 and up from the sump to be discharged into thetube 260.

'I'he boss 84' of the top plate 32' is provided with an upwardl openingdepression which is connected by va passage 21| in the'boss 94' with thesurface therein. 'I'he end of the tube' 26|) is extended over theVdepression v268 so that oil discharged from the tube 26| with therefrigerant will be deposited the gear section of the pump andthelowerhearlng for the shaft 96' in the base plate 8|l'.` Al-v though asuction po `similarto port i3!! pre viously described may be providedfor conducting refrigerant from the interior of the casing 20 to eitheror both pairs of the gears 86 and 882 in the present case a portion ofthe top plate 92' is kbroken away so that a relatively large area of thetop of one of the gears' 88' is exposed directly to the space within thehousing 20', and the refrigerant within the housing 20T is, therefore,fed to the spaces between the teeth of the gear 88' instead of through aseparate-i ly formed suction passage. ,Where the gear B6' and only onegear 8l' is employed,` and the tube .26D forms the sole suction conduitfor 'the'l refrigerating system, .allof the refrigerant circulated inthefsystem will be 'introduced to the pump through the` ends of thetooth spaces at 212.

evaporator 54 and onlyone ofthe evaporators 4|) previously described, ora similar arrangement, the suction tube 260 will, of course, beconnected to only y one of the evaporators, and the suction line for theother evaporator will be brought up` through the bottom of the baseplate lill' in a manner equivalent orfsimilar to that described inconnection with the preceding `:tlgures.

One feature ofthe present invention is brought out in Fig; 10, andthatis in` connection with y means for preventing excessive amounts oflubricating oil from passing through the compressor. 'I'his featurecomprises the'provision of an opening such as 214 leading through thewall of the compressor shown in Fig. l0, as through a wall of the body84 and opening to the lower periph-l eral portion of that gear 88y whichco-operates with the gear 86 to draw refrigerant from the interior ofthecasing 30' and thereafter compress it. The provision of such an opening214 would not Vbe applicable to `the pump formed by thegear 88 and gearB6" drawing the refrigerant through the bottom plate independently ofthe casing 20' where the casing 20' also serves as a part of arefrigerant fiow path for a separate evaporator, but where thecompressor comprises y 22,245 l .is bent in the direction tooth portionsofsuch gears and preferably extend outwardly from the outer edges of thecoso that theow of refrigerant of the pump 1n the depression rss and, jtherefore, be led to the bearing surface for the shaft 96 and be carriedthereby downwardly into operating'gears so that lubricating" oil trappedbetween the teeth of the gears` and carried by.

gravity ,to the/lower edges thereof will be either wiped oif or thrownoilr` under centrifugal force' into the passages 214 and dischargedfromthe pump, thus forming a centrifugal oil separator and preventing anymaterial amounts of oil from being carried through the systemcompressor. ,f r Formal changes may be made in the specific embodimentof the invention disclosed without outside of the -departing from thespirit or substance of the` brc-ad invention, the scope of which iscommen-` surate with the appended claims.

WhatrI claim is: A 1. In -a refrigerating mechanism.. in combination,refrigerant condensing means. provided with independent suction portsand adapted to 4simultaneously exert independent suction effectstherethrough, a pair of evaporators, means for .delivering refrigerantfrom said condensing means to said evaporators in parallel includingrefrigerant regulating means controlling the'iiow of refrigerant to oneof said evaporators and toa second refrigerant regulating means inseries Where two separate evaporators are employed, for instance, as inthe case where the with the first-mentionedregulating means and 'withthe other of said evaporators, a suction duct connecting one of saidevaporators to one of said suction ports, and a separate suction ductcon'-` necting the other of said evaporators with the other of saidsuction ports. I

2. In a refrigerating mechanism, in\ combina. tion, refrigerantcondensing means p'rovided with independent suction ports and adapted tosimul Vtaneously exert independent suction effects therethrough, a pairof evaporators, means for delivering refrigerant `from saidk condensingmeans to said evaporators in parallel including refrigerant regulatingmeans controlling the flow of refrigerant to one of said evaporators andto a second refrigerant regulating means .in series with -thefirstmention'ed regulating means and comprising a weighted valve deviceconnected with the other of said evaporators, a suction duct connectingone of said evaporators vto one of said suction ports,l and a yseparatesuction duct connecting the other of said evaporators with the other o fsaid suction ports.l

3. In a, refrigerating mechanism, in combinan, tion, a -sealed housing,a compressor, apart of merely a pair of gears having a single suctionport, or threegears having their suction ports combinedthen Yall ofthegearsmay be provided with openings equivalent to the openings 214.

The 214- may connect with the lowery said compressor forming a closurefor said housing. said compressor having a pair of independent `suctionports one drawing vapor from inside of said housing and one located in awall of said compressor at a point exposed outside of said housing, anda lpair of independent suction ducts for delivering refrigerant to saidsuctionports,

the interior of saidhousing forming a portion oi one of said suctionducts.

4. In a refrigerating system, a compressor so constructed and arrangedthat gas from the discharge side may return to the suction side thereofafter said compressor has stopped, a motor for driving said compressor,,a condenser into which said compressor is adapted to dischargecompressed refrigerant, a duct connecting said compressor and condenserfor the passage lof said refrigerant, and a check valve.located,in saidduct to prevent flow of vapor from said condenser to said compressor ina reverse direction, said duct being soconstructed and arranged in thatportion thereof between said compressor and said driving saidcompressor,

`said compressor is adapted to discharge coml constructed and arrangedthat gas from the discharge side may return tothe suction side thereofafter said compressor has stopped, a motor for a condenser into whichpressed refrigerant, a duct connecting said compressor and condenser forthe passage of said refrigerant, a check valve located in said 'duct toprevent flow of vapor from said condenser to said compressor in areverse direction, said duct being so constructed and arranged in thatportion thereof between said compressor and'said check valve as toprovide sufficient volume for compressed refrigerant starting toapproximately reach its running speed before the Apressure of-therefrigerant delivered by the compressor to said portion of said passageduring said starting equals the pressure of the refrigerant in saidcondenser, and means( for trapping oil in an intermediate portion ofsaid duct portion in such a to said compressor compressor.

6. In a refrigerating system,'a compressor and during the idle periodsof said a motor, a gas tight housing enclosing said compressor andmotor, said housing having .a pair of suction passages leadingthereinto, valve means for alternately opening and closing one of saidpassages as it closes and opens the other of said passages, and meansdriven by said motor4 actuating said valve means, said compressor havingan inlet port open to the interior of said housing.

7. In combination with a refrigerating system, a compressor comprising ahousing, a train of three gears in said housing, means for driving saidgears, said housing providing discharge ports located adjacent thepoints where the teeth of mating gears begin to engage and suction portsfor introducing gas' between the teeth of said gears, a pair ofevaporators, means connecting said evaporators with said dischargeports, means connecting one of said evaporators with one of j' saidsuction ports, and means independent of the last-mentioned meansconnecting the other of said evaporators with the other of said suctionports.

8. In a refrigerating system, a compressor, a f 'motor having a drivingconnection with said compressor, a sealed housing enclosing said drivingconnection, a plurality of evaporators, suction conduit means connectedwith the interior of said housing and with said evaporators, means forselectively connecting said evaporators with the suction side of saidcompressor through said conduit means, and power means driven by saidmotor for actuating said selective connecting means.

9. A compressor, an enclosure for suction gas connected therewith, valvemeans in said enclosure, and means for actuating saidl valve means withmechanical power derived from the operation of said compressor in acycle Imaterially longer than that of a compressor revolution.

10. In a refrigerating system, .a pair of evaporators, amotor-compressor unit, a sealed housing enclosing said unit, meansforming a pair of suction passages for conducting vaporized refrigcheckvalve as to provide a sumclent volume for compressedfrefrigerant-topermit'said motor upon der suction produced bythe compressor of said topermit said motor upon manner that it will be returned i verant fromsaid each of them, valve means for alternately opening and closingfoneof said passages as it closes evaporators, one connected to and opensthe other, and power means for actuatingV said valve means, said powermeans deriv` ing itsl energy from a` source enclosed in said hous- In arefrigerating system, a motor-compressor assembly, a sealed housingenclosing the moving parts of said assembly, a plurality of suctionconduits througlrwhich vapor may flow unassernbly, and means within saidhousing opervable automatically 'as' a result of the functioning of saidsystem for intermittently stopping the .flow of vapor through one ofsaid conduits for `a period of time considerably longer than that of arevolution of said compressor. -v 12. In a refrigerating system, a pairof evaporators each having a suction outlet conduit, a

compressor adapted for drawing vapor from said evaporators through saidsuction outlet conduits thereof, said conduits being connected inparallel, and a condenser connected with said compressor for receivingvaporfrom both said evaporators after it has' been compressed, saidcompressor being reversible during idle periods under the inuence ofrefrigerant under pressure on its dis#- charge side'whereby to enable itto relieve itself of said discharge `pressure during idle periods.

13. In a refrigerating system, a rotary compressor of the displacementtype, a motor for driving said compressor, a sealed housing enclosingthe moving parts pressor and adapted to contain a refrigerant circulatedin said system and a lubricant for said moving parts, and centrifugalmeans in said compressor for separating said lubricant from saidrefrigerant.

14. In a refrigerating system, a motor compressor assembly comprising amotor and a compressor and a driving connectionV therebetween, agas-tight housing enclosing said driving connection and the moving partsof said motor and compressor, a refrigerant suction duct. leading tosaid housing, a refrigerant suction duct leading to said compressor andopen to the interior'of said housing, and a refrigerant suctionductseparated from both aforesaid suction passages and leading directly to aseparate suction port of said compressor at an area thereof exposedoutside of said housing.

15. In a refrigerating mechanism, in combination, a compressor, a motor,a driving connection between said motor and said compressor, a housingsurrounding said motor and connection and sealed to said compressor witha face of said compressor exposed exteriorly of said housing and forminga gas-tight enclosure for said motor and connection, said compressorhaving a first suction port opening onto the interior of said housingand a second suction port opening onto the exterior of said face, saidsecond suction port adapted to be connected to a source of flow ofrefrigerant, said compressor having a discharge passage opening onto theexterior of said face, and said housing having a suction passageopeningthrough a wall thereof adapted for connection with a source of flow ofrefrigerant whereby to admit refrigerant therethrough into the interiorof said housing, whereby said interior of saidiousing forms a part ofasuction passage between said first suction port source of flow of reandthe second mentioned yfrigerant.

16, In a refrigerating mechanism of the class of said motor and com-Alwall thereof for receiving the flow wherein a hightemperature'evaporator allel refrigerant circuits, the combination withsaidparallel evaporators 0f common means for eli'ecting a iiow ofrefrigerant tion between said compressor and lotona hous- Iingsurrounding said motorand connection and sealed in vgas-tight yrelationto said compressor leaving a face of said compressor exposed exteriorlyof said housing, said compressor having a iirst suction port open to theinterior of said housing and said housing having of refrigerant fromsaid high temperature evaporator whereby the interior of said housingforms a part of uthe refrigerant passage between .said hightemperatherethrough comprisln'g a compressor, a motor, a drivingconnecaport in the l f aan and a low temperature evaporator areconnected in par ture evaporator and saidsuction port. said compressorhaving a second suction Port opening ontoy the exterior of said face fordirect connection to the other of said evaporators, and said compressorhaving a discharge port opening onto said face.

-1'I. In a refrigerating system, a motor compressor unit, a chamberassociated therewith, a plurality 'of evaporators each having a suctionpassage opening into said chamber, valve means in said chamber and valveactuating means for periodically opening and closing one of said suctionpassages as it closes and and power means energized by said compressorfor operating means. i

GLENN MUFFLY.

the operation of opens the' other,

said actuating

